What I'm saying is they often actually mean "country", but that is less fancy sounding. A nation-state is just one specific type of polity, certainly not the only type which organize attacks.
Not that "F5 announces attack by state sponsored hackers", "F5 announces attack by nation-state backed hackers", or "F5 announces attack from nationally backed hackers" have to be invalid, particularly since the latter is often what is actually most specifically correct anyways.